Wide frequency band amplifier



ug- 13, 1940- K. KUPFMULLER WIDE FREQUENCY BAND AMPLIFIER Filed June 11, 1936 -1 Lf A rbbbbbbb R E l RU Y O .E TWZJN T m L, I. R I A m Y E Patented Aug. 13, 1940 UNITED STATES PATENT OFFICE 2,210,981 WIDE FREQUENCY BAND AMPLIFIER Application June 11, 1936, Serial No. 84,666 In Germany June 14, 1935 1 Claim.

This invention relates broadly to amplifiers of the vacuum tube type for transmitting a wide frequency band, and more specifically to coupling means between the various tubes in order to accomplish the uniform transmission of the band.

In accordance with this invention, the width of the frequency band to be transmitted without distortion is increased in that the ordinary coupling members of the tubes are joined to inductive elements to form a transmission line comprising several members. Ordinarily, an amplifier circuit may have two of its tubes coupled together by means of two resistance elements joined together by a condenser in well knownfashion. In addition, to the aforementioned capacity, the width of the band has been limited by natural capacities existing between the anode and cathode of the tubes, distributed capacity of the coupling elements, capacities between leads etc. and itis the object of this invention to provide artificial means to be used in conjunction with the normal coupling elements so as to form a coupling unit of high fidelity adapted to transmit a wide frequency range.

By forming a transmission line of several members, it is possible, through suitable dimensioning, to extend the frequency limit of the coupling element as far upwards as may be desired. The individual members of the transmission line, according to my invention, will be designed so asto present an approximately equal Wave resistance to the frequencies to be amplified. The terminal resistances of a coupling member would advisably likewise have to be so dimensioned as to have approximately the wave resistance of the coupling member. If the proportion between inductances and capacitances of a coupling member is made approximately equal to the square of the terminal resistance, arrangements will be obtained corresponding electrically, up to a certain frequency, to homogeneous lines closed with their wave resistancce. In this case, the actions of the inductances and capacitances compensate each other.

Of course the same effect may be obtained by suitable dimensioning of inductances already present, or by suitable construction of the lines. My invention will be best understood by reference to the accompanying drawing in which Figure 1 shows schematically the circuit of an ordinary resistance coupled amplifier without showing the D. C. sources.

Figure 2 shows schematically an embodiment of my invention.

Figure 3 shows schematically a split anode with its portions connected in accordance with my invention.

In, Fig. 1, R1 is the internal resistance between the anode A and the cathode K of a tube loaded by the outer resistor Ra. The resistor Hg is placed in the input circuit of the following tube between the grid G and cathode K and is coupled to the 5 preceding tube by means of condenser C. All natural and circuit capacitances are in parallel to the resistances and also betweenthe layers of the coupling condenser and the cathode line. Natural capacities also exist between the electrodes of the tubes. In the drawing, these capacities are indicated in dash lines.

Fig. 2 shows the manner ofinserting the inductances according to'the invention in the coupling member of the previous diagram. The cou- 15 pling member in Fig. 1' can, for high frequencies, be substituted-by the circuit according to Fig. 2. L1, L2, L3 represent the additional inductances to be inserted in the lines in accordance with the invention in order to make up a member of the 20 7 transmission line. For some uses, it will be sum- 'cient to insert a few inductances, however, this may be extended considerably in making up the members comprising the transmission line. Of course the invention could be applied to coupling 25 members between the input circuit of a tube and a preceding transmitter arrangement or between the output circuit of a tube and some device to be operated thereby.

The features of the present invention can be 30 extended to the interior of the tubes, thus obtaining a further increase in the 'efiective frequency 7 range. If, for instance, the plate cylinder of a tube is divided into two or several longitudinal sections, a corresponding sub-division of the 5 plate-cathode capacity is therebyproduced. The sections thus obtained are connected to each other across coils as shown in Fig. 3 and included in the system of the line of constant wave resistance. Fig. 3 shows two sub-divisions of theanode struc- 40 ture as A1 and A2 connected to. each otherby means of coil L1. Coil L2 is inserted in the plate lead-in. 1

What I claim is:

An amplifier for transmitting a wide frequency 5 range comprising a vacuum tube having anode, cathode and control electrodes, said anode being comprised of a plurality of collecting elements, inductive elements joining said collecting elements, and an output circuit for said vacuum 5 tube; said output circuit comprising a transmis-. sion line consisting of a.plurality of members each having approximately the same wave resistance. I

KARL 55 

